Centrifugal switch mechanism



Oct. 16, 1956 J. H. FERGUSON 2,

CENTRIFUGAL SWITCH MECHANISM Filed July 18; 1955 United States Patent CENTRIFUGAL SWITCH MECHANISM John H. Ferguson, Hillsdale, N. J., assignor to Bendix Aviation Corporation, Teterboro, N. J., a corporation of Delaware Application July 18, 1955, Serial No. 522,667

3 Claims. (Cl. 200-80) The present invention relates to a centrifugal switch mechanism and more particularly to novel centrifugal force responsive means for actuating the switch mechanism.

An object of the invention is to provide a centrifugal switch including a novel electric brush holder adjustably mounted on a rotating member and responsive to centrifugal force to hold an electric brush under such force so as to maintain a good contact relation with a slip ring up to a predetermined driven speed of the rotating member at which a second centrifugal force responsive means overcomes the force applied to the brush holder to instantaneously actuate the brush out of contacting relation with the slip ring.

Another object of the invention is to provide anovel compact centrifugal force responsive .cutsolf switch of great efficiency in comparison to its size, and of such simplicity in construction as to adapt it for manufacture and installation at low cost.

Another object of the invention is to provide a novel centrifugal force responsive means for maintaining an electrical brush mounted on a rotating member in good contacting relation with a slip ring under high brush pressure up to a predetermined critical driven speed of the rotating member at which other novel centrifugal force responsive means mounted on the rotating member serves to effect instantaneous actuation of the brush holder to a position lifting the brush from contacting relation with the slip ring.

Other objects and advantages of this invention are set forth in the following description, taken with the accompanying drawings; and the novel features thereof are pointed out in the appended claims. The disclosure, however, is illustrative only and changes may be made in detail, especially in matter of shape, size and arrangement of parts within the principle of the invention to the full extent indicated by the broad and general meanings of the terms in which the appended claims are expressed.

In the accompanying drawings, which form a part of this specification, like characters of reference indicate like parts in the several views wherein:

Figure 1 is a perspective view of a rotary member on which is mounted the novel centrifugal switch;

Figure 2 is an end view of Figure 1 illustrating the centrifugal switch or brush actuating mechanism with the brush shown in contacting relation with a slip ring or electrical contactor;

Figure 3 is a sectional view of Figure 2 taken along the lines 33 and looking in the direction of the arrows.

Referring to the drawings, an arm 1 is pivoted on a pin 2 mounted on a rotating member 3. A resilient spring 4 is fastened at one end to the arm 1 and at an opposite end to a combination stop and spring fastening member 5. The spring 4 is under tension and tends to bias the arm 1 in a clockwise direction about the pin 2, as shown in Figures 1 and 2. A spring guard 6 may be provided to prevent excess distortion of the spring 4 at high speeds of rotation of the rotatable member 3.

2,767,273 Patented Oct. 16, 1956 A brush holder 7 is pivoted on a pin 8 projecting from the rotatable member 3. The holder 7 has a U-shaped portion into which an end of arm 1 fits, as shown in Figures 1 and 2, with a clearance 9. A resilient spring brush element 10 is attached to the brush holder 7 and may be electrically isolated or not, as desired. The brush 10 is arranged to contact a stationary slip ring 11, as shown in Figures 2 and 3, when the rotatable member 3 is at rest or rotated at a speed below a predetermined cut-out speed. The slip ring 11 may be electrically isolated from the brush holder 7 and separate electrical conductors may be arranged to lead from slip ring 11 and brush holder 7 so that when the brush 10 is in contacting relation with the slip ring 11, an electrical circuit may be closed and upon the brush 10 being raised out of contacting relation with the slip ring 11 the circuit may be opened.

There is further indicated by the numeral 12 a point at the center of rotation of the rotatable member 3, while the numerals 14 and 15 indicate centers of gravity of the respective members 1 and 7.

In operation, the spring 4 biases the arm 1 in a clockwise direction so as to bear down on one leg of the U- shaped brush holder 7 exerting a force on the brush 10, holding it against the slip ring 11. Upon rotation of the rotatable member 3 by a suitable driving member to which it may be connected, the rotatable member 3 will rotate around its center of rotation, indicated by the numeral 12, and the brush 10 will move around the stationary slip ring 11. As the speed of rotation of the rotatable member 3 increases, the centrifugal force on the arm 1 acting through its center of gravity, indicated by the numeral 14, will cause the arm 1 to exert less and less load on the brush holder 7.

As the speed of rotation of the rotatable member 3 increases, the brush holder 7 tends to rotate counterclockwise about its pivot point 8, as indicated by the arrow adjacent thereto, since its center of gravity, indicated by the numeral 15, is offset from the pivot point 8 so that centrifugal force acting on the brush holder 7 tends to increase the load applied on the resilient spring brush element 10. It can be seen then that as the arm 1 is releasing its load on the lower leg of the U-shaped brush holder 7 and thus decreasing the load applied by the arm 1 on the brush 10, the brush holder 7 acting under the centrifugal force resulting from the rotation of the rotatable member 3 will be applying an increasing load to the resilient spring brush element 10.

At a predetermined speed of rotation of the rotatable member 3, the centrifugal force on the arm 1 will just balance the load applied by the spring 4 and the arm 1 will no longer touch the lower leg of the U-shaped brush holder 7. As the arm 1 tends to rotate counter-clockwise, as indicated by an adjacent arrow, around its pivot 2 upon a further increase in such centrifugal force, the center of gravity, indicated by the numeral 14, will move out from the center of rotation 12 of the rotatable member 3, as indicated by dotted lines in Figure 3. The increase in centrifugal force aplied to the arm 1 due to this displacement of the center of gravity 14 outward from the center of rotation 12 will exceed the increase in spring load applied to the arm 1 by the spring 4 and the arm 1 will tend to move rapidly across the gap 9 between the lower and upper legs of the U-shaped member 7 until the free end of the arm 1 contacts the upper leg of the U-shaped brush holder 7 with a toggle action. The amount of toggle action between the arm 1 and the spring 4 is such that the bias on arm 1 due to the spring 4 is progressively reduced as arm 1 moves in a counterclockwise direction in response to centrifugal force about the pivot 2. Enough energy and load is available to overcome the centrifugal force of the displaced center of gravity 15 of the brush holder 7, causing the brush holder 7 to rotate in a clockwise direction under force of the arm 1 until it hits the stop 5. In this position the resilient spring brush element no longer contacts the slip ring 11, and the circuit closed by the brush 10 contacting the slip ring 11 is opened.

As the rotatable member 3 slows down to below the cut-off speed, the spring 4 will tend to bias the arm 1 so as to bring the brush holder 7 back into the original position, shown in Figure 2.

The operation of the foregoing switch arrangement is by centrifugal force and once the contacting relation between the brush 10 and the slip ring 11 is opened, the switch is capable of being driven to high speed, as there is no further motion in the switch. The switch mechanism may be designed for the grounding of one wire or multiple contacts, depending upon the number of stationary slip rings used. While the disclosure shows a switch using only one slip ring 11, a plurality of such slip rings and brushes 10 may, if desired, be added thereto.

Although only one embodiment of the invention has been illustrated and described, various changes in the form and relative arrangement of the parts, which will now appear to those skilled in the art, may be made without departing from the scope of the invention. Reference is, therefore, to be had to the appended claims for a definition 'of the limitation of the invention.

What is claimed is:

l. A centrifugal switch comprising a rotary member having a center of rotation, an arm, a first pin pivotally mounting said arm on said member at a point spaced from the center of rotation of the rotary member, a U- shaped brush holder, a second pin pivotally mounting said holder on said member at a point spaced from the center of rotation of the rotary member, an electrical brush carried by said brush holder, a slip ring, said brush normally cooperating with said slip ring in contacting relation, a spring biasing said arm into contacting relation with one leg of said U-shaped brush holder and in spaced relation to the other leg of said U-shaped brush holder so as to normally maintain said brush and slip ring in contacting relation, said arm having its center of gravity so arranged that upon the speed of rotation of said member exceeding a predetermined maximum value said arm under centrifugal force pivots on said first pin in opposition to said spring and out of contacting relation with the one leg of said U-shaped brush holder, said U-shaped brush holder having its center of gravity so arranged that said centrifugal force acts on said'brush holder so as to tend to bias said brush in a direction to maintain said brush in contacting relation with said slip ring, said arm under said centrifugal force moving outwardly from the center of rotation of said rotary member so as to displace the center of gravity of the arm outwardly from the rotational center of the rotary member so that the centrifugal force applied to said arm due to said displacement of the center of gravity of the arm exceeds the biasing force applied to said arm by the spring and causes said arm to strike the opposite leg of said U-shaped brush holder with sufficient force to actuate said brush holder in a sense causing said brush to be actuated out of contacting relation with the slip ring.

2. A centrifugal switch comprising a rotary member having a center of rotation, a first weighted member pivotally mounted on said rotary member at a point spaced from the center of rotation of the rotary member, a sec- 1 0nd weighted member pivotally mounted on said rotary member at a point spaced from the center of rotation of the rotary member, an electrical brush carried by said second weighted member, a slip ring, spring means biasing said first Weighted member in a first sense into contacting relation with said second weighted member so as to normally maintain said brush in contacting relation with said slip ring, said second weighted member having a center of gravity so arranged that upon rotation of said rotary member centrifugal force acts on said second weighted member so as to tend to bias said brush in a direction to maintain said brush in contacting relation with said slip ring, and said first weighted member having a center of gravity so arranged that upon the speed of rotation of said rotary member exceeding a predetermined maximum value centrifugal force actuates said first member in a second sense out of the first mentioned contacting relation with said second member and into a second contacting relation with said second member so as to actuate said second member so as to lift the brush out of contacting relation with the slip ring.

3. A centrifugal switch comprising a rotary member having a center of rotation, a first centrifugal force responsive means mounted on said rotary member at a first point spaced from the center of rotation of the rotary member, a second centrifugal force responsive means mounted on said rotary member at a second point spaced from the center of rotation of the rotary member, an electrical brush, a slip ring, said electrical brush cooperating with said slip ring and carried by said second centrifugal force responsive means, said second centrifugal force responsive means tending to bias said brush into contacting relation with said slip ring with a force increasing with the speed of rotation of said rotary memher, said second centrifugal force responsive means including means actuated by said first centrifugal force responsive means upon the speed of rotation of the rotary member exceeding a predetermined maximum value to raise said brush out of contacting relation with said slip ring.

No references cited. 

